High-precision travel-time monitoring with seismic reflection techniques
Abstract
The feasibility of using controlled-source reflection and refraction methods for travel-time monitoring is discussed. Travel-time changes, if any, that may be detectable with such measurement techniques are described. Travel-times were measured at sites in two areas south of Hollister, California, along the creeping zone of the San Andreas fault using a single-channel system with real-time on-site data processing. Events at 7 to 8 sec travel-time were monitored at sites about 7 km from the San Andreas fault in Bickmore Canyon in both short-term experiments spanning a number of hours and in a long-term series of measurements spanning two years. Two major types of noise were identified. Scattering of the short-term data, believed to be due to source variations, limits the measurement precision to about 0.01 percent of the travel-time for the deep reflections and about 0.1 percent for the first arrivals. Secondly, the dominant features of the long-term data sets are persistent, rainfall-related, seasonal oscillations in travel-time (of as much as 15 to 20 msec peak-to-peak), wavelet amplitude and waveform.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1980
- Bibcode:
- 1980PhDT........40C
- Keywords:
-
- Earthquakes;
- Seismic Waves;
- Time Measurement;
- Transit Time;
- Traveling Waves;
- Earth Movements;
- Geological Faults;
- Seismology;
- Geophysics